Composite softball bat with inner sleeve

ABSTRACT

A softball bat is made substantially out of composite material. The main portion of the bat includes a substantially tubular hitting surface, a taper, and a handle. A plurality of sleeves are added within the hitting surface to form a flexible bat.

RELATED APPLICATIONS

[0001] This application is a divisional of U.S. patent application Ser.No. 10/438,196 filed May 14, 2003, which is a continuation-in-partapplication of U.S. patent application Ser. No. 09/883,790 filed on Jun.18, 2001, which claims priority under 35 U.S.C. 119(e) from U.S.Provisional Application Ser. No. 60/263,020 filed Jan. 19, 2001, whichapplications are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to the field of bats and moreparticularly to a softball bat.

BACKGROUND OF THE INVENTION

[0003] For many years softball bats were made of wood. Traditionalathletic bats comprised of wood are expensive and consume valuablenatural resources. A disadvantage of wood bats is that they frequentlybreak during use. A further disadvantage of wood bats is that they areexceedingly difficult to design for consistent performance, given theinconsistency of the natural material. In addition, wooden bats are madeof ash or very hard pine. The sources of such woods are becomingincreasingly scarce.

[0004] In the past fifteen or twenty years, softball bats made of metalwere introduced. Metal bats, although more durable than wood bats, alsohave problems. One of the many problems associated with a metal bat isthat the material is fixed and, as a result, so are the parameters ofthe material. Metal bats have a fixed density and a given weight. As aresult, the engineering parameters that can be varied can only be variedwithin a limited range.

[0005] Currently, metal softball bats are more commonly used than woodensoftball bats. A common structure in various non-wooden softball batsincludes a hollow bat made with a handle and a hitting surface. Thehitting surface includes a tubular portion and a sleeve fit inside thetubular portion. The sleeve is also made of metal. The metal bat andsleeve construction has problems. Several of the problems associatedwith metal softball bats having metal sleeves stems from the impact orlarge shock load exerted on the metal bat as a result of hitting thesoftball. The shock loading produces extremely large forces between thebat and the ball. The result is that the metal bat dents when a ball ishit. In other words, the metal may dent in some form when the ball ishit. Some dents are small and some dents are large. Regardless of thesize of the dent, energy is lost every hit since some of the energy isused to dent the metal rather than transferred to the softball. Thedents also result in a less durable bat. Once dented, each subsequenthit is a further cold working of the metal. In some instances, amicroscopic crack can also be formed as the result of denting of thebat. The crack will get bigger and bigger until the amount of materialleft fails due to shock loading. Many bats fail quickly. Some bats mayfail after as few as twenty-five hits.

[0006] More recently, composite bats have been introduced. Compositebats include a reinforced plastic with a metal portion. For example,U.S. Pat. No. 4,546,976 which issued to T. N. Jones on Oct. 15, 1985,discloses a reinforced plastic bat with a separate handle section thatis softer than the hitting section. Another example is U.S. Pat. No.4,569,521 which issued to A. W. Mueller on Feb. 11, 1986, whichdiscloses a composite bat having a tapered aluminum spar encased inpolyurethane foam in order to provide stiffness and freedom fromexcessive vibrations. Currently, composite bats have composite shellsand metal inner sleeves in the hitting portion of the bat. These batshave some of the same problems as a metal bat. In a composite bat, themetal sleeves dent over time and the impact energy that should betransferred to the ball is absorbed by denting the metal sleeve.

[0007] U.S. Pat. No. 5,722,908 issued to Feeney et al. on Mar. 3, 1998,discloses a composite bat with a metal barrel, and a method offabricating same. The bat has a frame having a recess and fabricated ofa composite material of fibers in a matrix binder. A metal sleeve isinserted over the recess of the frame, which forms a hitting surface.

[0008] What is needed is a more durable softball bat. What is alsoneeded is a bat which will not dent so that more energy is transmittedor applied to the softball. Another way of looking at this is that whatis needed is a bat which will not dent so that little or no energy iswasted denting the bat. Also needed is a bat which will not dent or becold worked such that an inherent weak spot is formed.

SUMMARY OF THE INVENTION

[0009] A softball bat is made entirely out of composite material. Themain portion of the bat includes a substantially tubular hitting surfaceand a handle. A composite sleeve is added within the hitting surface.The sleeve is made of composite material. The hitting surface is alsomade of composite material.

[0010] Advantageously, the composite material has a lower density thanmetals used to make bats, such as aluminum or titanium. As a result,more material can be used resulting in a more durable bat for a givenweight of bat. The composites also have a higher strength than aluminumand titanium and their alloys. Therefore, a stronger bat can beproduced. In addition, the composite does not dent and therefore moreenergy is transferred to the ball. There is less, if any, energy wastedon denting the bat or the inner sleeve. Therefore, the inventive bathits farther than a wooden or metal bat or bat having metal parts. Theinventive bat is made entirely of composite material. Composite materialcan be made either more stiff or more flexible than a metal bat. Thedesign parameters of a composite are more flexible so that either a moreflexible or stiffer bat can be formed by varying the engineeringparameters. The additional flexibility in using composite materialallows designers to form bats with selected performance characteristics.If the bat is made to be more flexible, the inventive bat has adurability advantage since the bat does not dent and begin the somewhatslow process of failing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a perspective view of a ball bat, with a portion of thetubular hitting surface broken away to show a sleeve according to thepresent invention.

[0012]FIG. 2 is a longitudinal sectional view of the ball bat of thepresent invention with the end cap exploded away and showing thecomposite inner sleeve.

[0013]FIG. 3A is an enlarged cross section view of the present inventiondrawn along lines 3A-3A of FIG. 2.

[0014]FIG. 3B is an enlarged cross section view along line 3B-3B in FIG.2.

[0015]FIG. 3C is an enlarged cross section view along line 3C-3C in FIG.2.

[0016]FIG. 4A is a plan view of the two initial fiber socks of the bat.

[0017]FIG. 4B is a plan view of the shortened fiber sock placed over theinitial sock layers shown in FIG. 4A.

[0018]FIG. 4C is a plan view of the fiber socks of the bat shown in FIG.4B with an added hoop wrap at the tapered portion of the bat.

[0019]FIG. 4D is a plan view of the fiber socks of FIG. 4C after beingcovered by another sock.

[0020]FIG. 4E is a plan view of the fiber socks of the bat shown inFIGS. 4A-4D with a hoop wrap added to the handle and part of the taperedportion of the bat.

[0021]FIG. 5 is an exploded perspective view of a set of sheetspre-impregnated fibers and a mandrel used to form the inner sleeve ofthe present invention.

[0022]FIG. 6 is a plan view of the fiber layers on the mandrel beingwrapped with a layer of tape.

[0023]FIG. 7 is a cross sectional view of the mandrel with a set ofsheets and three layers of tape wrapped around the mandrel.

[0024]FIG. 8 is a perspective cutaway view of the fiber layers in thesleeve.

[0025]FIG. 9 is a longitudinal sectional view of another embodiment ofthe ball bat of the present invention with the end cap exploded away andshowing the composite inner sleeve.

[0026]FIG. 10 is an enlarged cross section view along line 10-10 in FIG.9.

[0027]FIG. 11 is an exploded perspective view of a set of sheetspre-impregnated fibers and a mandrel used to form the inner sleeve ofthe present invention.

[0028]FIG. 12 is a plan view of the fiber layers on the mandrel beingwrapped with a layer of tape.

[0029]FIG. 13 is a cross sectional view of the mandrel with a set ofsheets and three layers of tape wrapped around the mandrel.

[0030]FIG. 14 is a perspective cutaway view of the fiber layers in thesleeve.

[0031]FIG. 15 is a perspective view of a set of sheets wrapped about amandrel used to form a bat according to another embodiment of theinvention.

[0032]FIG. 16 is a top view of a sheet of layup material used in oneembodiment of a bat.

[0033]FIG. 17 is a top view of a mandrel like the one shown in FIG. 15within a mold for a bat.

[0034]FIG. 18 is a schematic view of one embodiment of a fixture formeasuring the flexibility of a bat.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0035] In the following detailed description of the preferredembodiments, reference is made to the accompanying drawings, which forma part hereof, and in which are shown by way of illustration specificembodiments in which the invention may be practiced. It is to beunderstood that other embodiments may be utilized and structural changesmay be made without departing from the scope of the present invention.

[0036] The invention described in this application is useful with allmechanical configurations of bats including softball bats and baseballbats. FIG. 1 is an exploded view of one type of a bat 100 having asubstantially tubular hitting surface 110 and a handle 120. The ball bat100 is made of composite material. The main portion of the bat 100includes a substantially tubular hitting surface 110. A handle 120 isattached to the hitting surface. The handle 120 and barrel are integralin the bat shown in FIG. 1. It should be noted that the bat could beformed of a separate handle 120 and tubular hitting surface or barrel110. The tubular hitting surface 110 and the attached handle 120 formthe body 140 of the bat. The diameter of the handle 120 is less than thediameter of the tubular hitting surface 110 and therefore the body 140of the bat includes a tapered portion 114 which is positioned betweenthe handle 120 and the tubular hitting surface 110. A composite sleeve112 is added within the body 140 of the bat and more specifically withinthe tubular hitting surface 110.

[0037] The sleeve 112 of the bat 100 is also made of composite material.Therefore, both the hitting surface 110 and the sleeve 112 are made ofcomposite material. The inner sleeve 112 fits inside the hitting surface110 of the bat 100. The inner sleeve 112 is made of a composite materialwhich includes a fiber and a resin. The fibers can be made of Kevlar,graphite, carbon, boron, rayon, nylon, fiberglass, other plastics orother polymer materials. Graphite nano tubes may also be used. The resinor binding material may include thermosetting resin systems, epoxies,ceramics, or thermoplastics. The fibers are impregnated with a resin toform a composite material. A plug 130 is molded to the free end of thehitting surface 110. The plug 130 is typically molded into the free endof the bat 100 using a separate process.

[0038]FIG. 2 shows the bat 100 assembled and partially cut away alongthe length of the bat 100. The sleeve 112 is positioned within thesubstantially tubular hitting surface 110. In other words, the barrel ofthe bat is hollow. In the embodiment shown, the sleeve 112 is placed sothat it tightly fits within the barrel or tubular batting surface 110.The plug 130 is also molded into the free end of the bat 100. The bat100 is formed and made according to a resin transfer molding process.

[0039] The body 140 of the bat 100 is comprised of a continuous resinmatrix reinforced with a plurality of circumferentially-extending fibersocks 324, 326, shown in FIGS. 3A, 3B, 3C and 4 and two hoops 340, 342.In the preferred embodiment, the resin components consist of Epic S7311part A and part B available from Epic Resins of Omera, Wis., althoughother resin components may be used in alternative embodiments. Also, inthe preferred embodiment the fiber socks 324, 326 are cross woven andare comprised of 74% glass fiber and 26% carbon fiber, by weight. Ofcourse, other types of weaves and other fibers may be used inalternative embodiments.

[0040] This particular combination of resin components and fiber socks324, 326 results in a high-strength yet flexible body 140. When a ballimpacts the bat 100 during the batter's swing, the bat undergoes alocalized deformation conforming to the contact area of the ball, aswell as radial or hoop deformation (i.e., the cylindrical battemporarily deforms into an oval when viewed in cross section). Thisdeformation provides a springboard or trampoline effect which furtherenhances the hitting zone of the bat 100 and provides maximum velocityto the ball when hit by the bat. The trampoline effect provides distanceto a particular hit.

[0041] In the preferred embodiment, three fiber socks 324 a fiber sock326 and two hoop wraps 340, 342 are used to form the body 140 of the bat100. The fiber socks 324 are concentrically arranged within the resinmatrix of the body 140. FIGS. 4A to 4E illustrate the various layers ofthe bat as the bat is built up. As shown in FIG. 4A, initially two fibersocks 324 are placed on a mandrel. The two fiber socks 324 cover thebody of the bat. As shown in FIG. 4B, a sock 326 is placed over thehandle 120 and a portion of the tapered portion of the body of the bat.The next step, shown in FIG. 4C, is a hoop wrap 340 around the taperedportion of the bat and specifically around the two socks 324 andshortened sock 326. A first hoop wrap 340 is done with carbon fiber wrapwhich is advanced {fraction (3/32)} inches per wrap. The first hoop wrap340 covers the tapered portion of the body 140 of the bat. The hoop wrap340 reduces the bulk of the socks 324, 326 and provides added strengthto the tapered portion of the finished bat. The hoop wrap 340 is donewith carbon fiber wrap which is advanced {fraction (3/32)} inches perwrap. As shown in FIG. 4D, after the initial hoop wrap 340, anotherfiber sock 324 is placed over the body 140 of the bat. As shown in FIG.4E, a second hoop wrap 342 is then placed over the bat and overlaps aportion of the first hoop wrap 340. The second hoop wrap 342 is doneover the handle 120 of the bat and adds strength to the finished bat.The second hoop wrap 342 over the handle 120 removes bulk from the threesocks 324 and the sock 326. The hoop wrap 342 is done with carbon fiberwrap and advanced {fraction (3/32)} of an inch per wrap. The three socks324 substantially extend the entire length of the body 140 of the bat100, while the sock 326 substantially extends the length of the handle120 and through a portion of the taper. The tubular hitting surface 110is also referred to as a barrel. It should be noted the number of sockscan be increased or decreased depending on the design parameters.

[0042] In other words, the handle 120 and the tapered area between thebarrel 110 and handle 120 are hoop wrapped about the periphery of thosesurfaces.

[0043] Once the fiber socks 324, 326 are placed on the mandrel and hoopwrap 340, 342 as discussed above, and the mandrel as wrapped, is placedinto a mold where resin is injected into the mold. The mold is placed ina press.

[0044] After curing, the mandrel and bat is removed from the mold. Thebat is cut to length. The sleeve 112 is then force fit within the barrelor hitting surface 110 of the bat.

[0045] Since the sleeve 112 is made of a composite, the sleeve alsoprovides a trampolining effect in addition to the trampolining effect ofthe tubular hitting surface 110 of the bat 100. The sleeve 112 is formedof a composite which is more stiff than the composite forming thetubular hitting surface 110 of the bat 100. Like the tubular hittingsurface 110, the deformation of the sleeve 112 conforms to the contactarea of the ball. The deformation of the sleeve 112 results in radial orhoop deformation where the sleeve 112 temporarily deforms into an oval,when viewed in cross section. Deformation of the sleeve 112 provides anadditional springboard or trampoline effect which is in addition to thespringboard or trampoline effect associated with the tubular hittingsurface 110 of the bat 100. The trampolining effect of the sleeve 112further enhances the hitting zone of the bat 100 and provides additionalvelocity to the ball when hit by the bat 100. The trampoline effectprovides distance to a particular hit.

[0046] The inner sleeve 112 placed inside the barrel or tubular hittingsurface 110 of the bat 100 is made out of a different materials thanthose used in the body 140. The sleeve 112 includes sheets of inlineimpregnated fibers also called pre-impregnated (some referred to aspre-preg) material. A series of sheets 500 are laid up to form thelayers of the inner sleeve 112. The inner sleeve 112 is substantiallycylindrically shaped.

[0047] As shown in FIG. 5, the sleeve 112 is formed by placing theseries of four sheets 500 on a cylindrical mandrel 520. There are fourlayers of lay up which form the series of sheets 500. Two of the layers501, 502 are at plus or minus 45 degrees. The layer 503 is at 90 degreesand the last layer 504 is at 0 degrees. The fibers within theimpregnated or pre-impregnated material are at 0 degrees when they aresubstantially aligned with a longitudinal axis 522 of the mandrel 520 ora longitudinal axis of the cylinder of the sleeve 112. The fibers withinthe impregnated or pre-impregnated material may also be said to be at 0degrees when they are substantially aligned with an axis of the bat 100running from the center of the tubular end 110 to the center of thehandle end 120. The four layers 501, 502, 503, 504 are E-glass fiberimpregnated with resin. It should be noted that the sheets 501, 502,503, 504 can also be any fiber and resin system. It should be noted thatthe layup angles can change as well as the number of layers and still bewithin the scope of the invention. For example, in some embodimentslayers 501 and 502 may be included in a single sheet.

[0048] After the four sheets of pre-impregnated material are placed ontothe mandrel, three layers of tape are placed on the four layers ofpre-impregnated material as shown in FIGS. 6 and 7. The three layers oftape keep the four layers of pre-impregnated material 501, 502, 503, 504tight, to remove voids and remove air pockets. The first layer 601 oftape is a polypropylene tape that is put on with a lead, with a force onthe leading edge of approximately 12 to 13 pounds. The first layer 601of tape is ⅝″ wide. The first layer 601 of tape is wound over the fourlayers of pre-impregnated material with {fraction (3/64)}″ of feed and{fraction (37/64)}″ overlap. The first layer 601 of tape is actually puton in order to provide a release layer for the sleeve 112. The firstlayer 601 of polypropylene tape is available from any composite materialsuppliers.

[0049] After the first layer 601 of tape is placed on the mandrel, asecond layer 602 and a third layer 603 of nylon tape are then placed onthe mandrel over the first layer 601. The second layer 602 and thirdlayer 603 are nylon tape which provides more pressure which in turnmakes a stronger part. The second layer 602 and third layer 603 of nylontape are available from any composite material suppliers. The secondlayer 602 and the third layer 603 are each wound onto the previous layerof tape in a similar way as the first layer 601. The second layer 602and the third layer 603 are wound over the four layers ofpre-impregnated material and the first layer 601 with {fraction(37/64)}″ of an overlap. The second layer 602 and the third layer 603nylon tapes are also ⅝″ wide. The force on the leading edge of the tapeis increased for the second layer 602 and the third layer 603 to 15pounds of lead pressure or pressure on the leading edge. These secondlayer 602 wrap and the third layer 603 wrap provide strength to thebacking and removes any voids and any air pockets that might weaken thesleeve 112 as formed. The second layer 602 and the third layer 603generally strengthens the bat sleeve 112.

[0050] The arrangement on the mandrel 520, including the layers 501,502, 503, 504 of pre-impregnated material is then placed into an ovenwhere it is cured for approximately three hours to ensure that the finalproduct is cured. It is recommended that the curing take place for anhour on the pre-impregnated fibers, but curing is done for three hoursjust to make sure that the sleeve 112 is fully cured. After curing, thesleeve 112 is removed from the mandrel 520. The tape 601, 602, 603 isthen removed by merely cutting it off with a utility knife. The firstlayer 601 polypropylene tape on the inside of course provides a releaseagent so the layers 601, 602, 603 release very easily from the sleeve.

[0051]FIG. 8 is a perspective cutaway view of the fiber layers in thesleeve. The perspective cutaway view of the sleeve 112 shows the variousdirections of the individual layers 501, 502, 503 and 504 within thecured sleeve 112.

[0052] The next step is to grind off enough of the exterior of thesleeve 112 so that it can be force fit within the barrel or the tubularhitting portion 110 of the bat 100. Even though the sleeve 112 is forcefit within tubular hitting portion 110 of the bat 100, the outer skin ortubular hitting surface 110 is able to flex and bend and elasticallydeform and act like a springboard or trampoline for the ball. The sleeve112 also provides a trampolining effect. In addition, the sleeve 112provides strength and endurance for the shock loading associated withhitting the ball. The sleeve 112 helps launch the ball. Others maydescribe the bat 100 as having the capability of giving the ball “pop”upon a hit.

[0053] It should be noted that there are many different ways toconfigure the fibers within the body 140 and within the sleeve 112. Oneidea is to configure the fibers within the body 140 and within thesleeve 112 so that the vibrational nodes associated with hitting a ballwith the bat are away from the handle 120 of the bat. In other words,the fibers within the body 140 and within the sleeve 112 may be changedto tune the bat 100 so that when a user hits the softball at variouspositions on the tubular hitting surface 110, the vibrational nodeswould not be in the handle 120 of the bat. If the vibrational nodes canbe moved from the handle 120, then there would be little or no “sting”or the vibration transmitted to the user's hands.

[0054] Of course, different lay-ups of materials can be used in formingthe sleeve 112. Furthermore, different types of materials can be used informing the body 140. Changing materials or the angles of the fiberswithin the bat and sleeve are considered within the invention. Changingthe shape of the bat 100 or using a different backing for the sleevehave also been contemplated.

[0055] It should also be noted that the body 140 of the bat 100 could bemade with a composite barrel or hitting surface 110 and the handle 120and taper could be made of another material such as metal. A sleeve 112could then be placed within the barrel or hitting surface 110 and thiswould still be within the scope of this invention. Although thepreferred embodiment describes the entire body 140 of the bat 100 madeof composite, it is contemplated that the tapered portion of the body140 and the handle 120 of other material could be substituted and bewithin the scope of this invention where the hitting surface 100 ofcomposite includes a composite sleeve 112.

[0056] Another bat 900 will now be discussed with respect to FIGS. 9-13.There are several differences between the bat 900 and the bat 100previously described. One of the differences is that there are multiplesleeves within the bat. In other words, multiple sleeves replace thesingle sleeve shown in FIGS. 1-8. As shown in FIGS. 9 and 10, there area plurality of sleeves 1050, 1060 placed within the tubular hittingsurface 324 of the bat 900. The plurality of sleeves 1050, 1060 have acombined wall thickness substantially the same as the wall thickness ofthe single sleeve 112 shown in FIGS. 1-8. The plurality of sleeves 1050,1060 are more flexible than a single solid sleeve. An analogy can bedrawn to a phone book. A phone book with its multiplicity of pages ismore flexible than a solid block of wood. Similarly, a number of sleeves1050, 1060 is more flexible than a single solid sleeve. It should benoted that although only two sleeves 1050, 1060 are shown in FIGS. 9-10,it is contemplated that additional sleeves could be used and this iswithin the scope of the invention. The flexibility afforded by multiplelayers is balanced with the required strength to determine anappropriate number of layers.

[0057] As shown in FIG. 11, the sleeves 1050, 1060 are formed by placingthe series of five sheets 1101, 1102, 1103, 1104, 1105 on a cylindricalmandrel 1020. Two layers of lay up 1101, 1102 form the first sleeve 1050and two layers of lay up 1104, 1105 form the second sleeve 1060. Arelease layer 1103 is positioned between the first sleeve 1050 and thesecond sleeve 1060. The release layer 1103 between the first sleeve 1050and the second sleeve 1060 is made of polypropylene or another suitablerelease material. The release layer 1103 is a sheet of polypropylene orrelease material that is placed between sheets 1102 and 1104 in the layup. The layer of polypropylene provides for a more flexible bat and morespecifically a more flexible hitting surface. The layers 1101, 1102 ofsleeve 1060 are at plus or minus 30 degrees. The layers 1104, 1105 ofsleeve 1050 are also at plus or minus 30 degrees. The fibers within theimpregnated or pre-impregnated material are at 0 degrees when they aresubstantially aligned with a longitudinal axis 1022 of the mandrel 1020or a longitudinal axis of the cylinder of either the sleeve 1050 or thesleeve 1060. The fibers within the impregnated or pre-impregnatedmaterial may also be said to be at 0 degrees when they are substantiallyaligned with an axis of the bat 100 running from the center of thetubular end 110 to the center of the handle end 120. The four layers1101, 1102, 1104, 1105 are carbon fiber impregnated with resin. Itshould be noted that the sheets 1101, 1102, 1104, 1105 can also be anyfiber and resin system. It should be noted that the layup angles canchange as well as the number of layers and still be within the scope ofthe invention. For example, in some embodiments, two layers may beincluded as a single sheet.

[0058] After the four sheets of pre-impregnated material 1101, 1102,1104, 1105 and the layer of release material 1103 are placed onto themandrel, three layers of tape are placed on the five layers as shown inFIGS. 12 and 13. The three layers of tape keep the four layers ofpre-impregnated material 1101, 1102, 1104, 1105 and the layer of releasematerial 1103 tight and removes voids and air pockets from the lay up.The first layer 1201 of tape is a polypropylene tape that is put on witha force on the leading edge of approximately 7.5 pounds. The first layer1201 of tape is ⅝″ wide. The first layer 1201 of tape is wound over thefive layers 1101, 1102, 1103, 1104, 1105 of material with {fraction(3/64)}″ of feed and {fraction (37/64)}″ overlap. The first layer 1201of tape is actually put on in order to provide a release layer for thefirst sleeve 1050. The first layer 1201 of polypropylene tape isavailable from any composite material suppliers. Of course, it should beremembered that the amount of tension may be changed based on materialand thickness of the material used to form the bat.

[0059] After the first layer 1201 of tape is placed on the mandrel, asecond layer 1202 and a third layer 1203 of nylon tape are then placedon the mandrel over the first layer 1201. The second layer 1202 andthird layer 1203 are nylon tape which provides more pressure which inturn makes a stronger part. The second layer 1202 and third layer 1203of nylon tape are available from any composite material suppliers. Thesecond layer 1202 and the third layer 1203 are each wound onto theprevious layer of tape in a similar way as the first layer 1201. Thesecond layer 1202 and the third layer 1203 are wound over the fourlayers of pre-impregnated material and layer of release material 1101,1102, 1103, 1104, 1105, and the first layer 1201 with {fraction(37/64)}″ of an overlap. The second layer 1202 and the third layer 1203nylon tapes are also ⅝″ wide. The force on the leading edge of the tapeis increased for the second layer 1202 and the third layer 1203 to 15pounds of lead pressure or pressure on the leading edge. The secondlayer 1202 wrap and the third layer 1203 wrap provide strength to thebacking and remove any voids and any air pockets that might weaken thesleeves 1050, 1060 as formed. The second layer 1202 and the third layer1203 generally strengthen the bat sleeves 1050, 1060.

[0060] The arrangement on the mandrel 1020, including the layers 1101,1102, 1104, 1105 of pre-impregnated material and the release layer 1103is then placed into an oven where it is cured for approximately threehours to ensure that the final product is cured. It is recommended thatthe curing take place for an hour on the pre-impregnated fibers, butcuring is done for three hours just to make sure that the sleeves 1050,1060 are fully cured. After curing, the sleeves 1050, 1060 are removedfrom the mandrel 1020. The tape 1201, 1202, 1203 is then removed bymerely cutting it off with a utility knife. The first layer 1201polypropylene tape on the inside of course provides a release agent sothat all layers 1201, 1202, 1203 release very easily from the secondsleeve 1060.

[0061]FIG. 14 is a perspective cutaway view of the fiber layers in thesleeve. The perspective cutaway view of the sleeves 1050, 1060 shows thevarious directions of the individual layers 1101, 1102, 1104 and 1105within the cured sleeves 1050, 1060.

[0062] The next step is to grind off enough of the exterior of thesleeves 1050, 1060 so that it can be force fit within the barrel or thetubular hitting portion of the bat 900. Even though the sleeves 1050,1060 are force fit within the tubular hitting portion of the bat 900,the outer skin or tubular hitting surface is able to flex and bend andelastically deform and act like a springboard or trampoline for theball. The sleeves 1050, 1060 also provide a trampolining effect. Inaddition, the sleeves 1050, 1060 provide strength and endurance for theshock loading associated with hitting the ball. The flexibility of thesleeves 1050, 1060 launches the ball. Others may describe the bat 900 ashaving the capability of giving the ball “pop” upon a hit.

[0063] Of course, different lay-ups of materials can be used in formingthe sleeves 1050, 1060. Also, more than two sleeves can be made forfitting within the hitting surface of the bat 900. Furthermore,different types of materials can be used in forming the body 140 of thebat 900. Changing materials or the angles of the fibers within the batand sleeves are considered to be within the scope of this invention.

[0064] It should also be noted that the body 140 of the bat 900 could bemade with a composite barrel or hitting surface 110 and the handle 120and taper could be made of another material such as metal. Sleeves 1050,1060 could then be placed within the barrel or hitting surface 110 andthis would still be within the scope of this invention. Although thepreferred embodiment describes the entire body 140 of the bat 900 madeof composite, it is contemplated that the tapered portion of the body140 and the handle 120 of other material could be substituted and bewithin the scope of this invention where the hitting surface 100 ofcomposite includes a composite sleeve 112.

[0065]FIG. 15 is a perspective view of a set of sheets ofpre-impregnated fibers positioned on a mandrel used to form a bat. InFIG. 15, the mandrel 1520 has a center line 1522. The mandrel 1520 iselongated and has a length approximately equal to the barrel orsubstantially tubular hitting surface 110. In this particular embodimentof the bat, longer sheets of prepreg material are used to form thebarrel of the bat right onto the mandrel 1520. The mandrel 1522 with thelayers of prepreg material and layers of polypropylene is then placeddirectly into a mold 1700 and injected with an appropriate resinmaterial to form the bat. The mold 1700 is shown in FIG. 17. After thebat is formed, it is removed from the mold 1700 and then the mandrel1520 is removed from the bat as formed so that a separate set of sleevesor a separate sleeve is not formed and then placed into the barrel ofthe bat after it has been molded. The advantage with respect to thisembodiment of the invention is that an entire set of steps is removedfrom the manufacturing process. In other words, a separate sleeve doesnot have to be formed and then placed inside the barrel of the bat butrather, in this embodiment of the invention, the bat is molded rightaround the mandrel. The layup of the various layers is similar to thatshown in FIG. 11 which is used to form a separate sleeve in anotherembodiment. Now turning to FIGS. 15 and 17, the end of the mandrel 1520which is near the tapered portion 1714 of the mold which corresponds tothe taper on the finished bat, is also tapered so as not to produce aweak spot in the molded material which is placed over the mandrel andover the layers that are laid up atop the mandrel. In other words, themandrel 1520 has an end 1720 which has a feathered layer of severallayers of material used to form the bat. The feathering prevents athinner portion in the wall of the bat near the end of the mandrel ornear the end 1720 of the mandrel that is near the taper 1714. The end ofthe mandrel is tapered or feathered and more specifically, the end ofthe layer atop the mandrel is layered or feathered so that there is noweak portion or weak spot formed.

[0066]FIG. 16 shows a top view of a sheet used to wrap about the mandrel1520. The sheet 1600 is cut into two portions 1610 and 1620. The sheetis cut along a diagonal line 1630. The dimensions of 1610 and 1620 areset so that the two halves, when rolled or applied to the mandrel 1520,will roll on with a taper due to the diagonal cut. The ends 1612 and1622 of the sheet will each be laid up on the end of the mandrel whichis toward the end of the barrel of the bat. The portion along thediagonal cut 1620 will be laid up or placed at the end 1720 of thelayers or of the mandrel 1520. Advantageously, by making a diagonal cutwhen the layers are placed upon the mandrel, it is self-tapering.Furthermore, by placing the cut, the sheets 1600 used to form the layupon the mandrel 1520, can be made to be self-tapering without wasting anyextra material. The length of the sheet 1610 between the end 1612 andthe cut line 1630 is shorter than the length between the end 1622 andthe cut line 1630. Therefore, the portion 1620 will be placed on themandrel 1520 first and rolled on and the edge 1630 will self-feather orself-taper. The other sheet 1610 will be then placed on the mandrel andthe longest dimension between the end 1612 and the cut line 1630 will beused as the starting point so that the sheet or portion of the sheet1610 will also self-feather as it is placed upon the previous sheet andthe mandrel 1520.

[0067]FIG. 18 is a schematic view of one embodiment of a fixture 1800for measuring the flexibility of a bat 1810. The fixture 1800 includes abase 1820 which includes an upright 1822 attached to the base and adatum 1824 also attached to the base 1820. The datum 1824 is spaced awayfrom the upright 1822. Attached to the upright 1822 is a load arm 1830.The upright 1822 has an opening 1823 therein. The load arm 1830 isattached to the upright by a pivot pin 1832. The pivot pin 1832 allowsthe attached end of the load arm 1832 to pivot about the opening 1823 inthe upright 1822. A dial indicator 1840 is positioned between theupright 1822 and the datum 1824 and near the load arm 1830. The dialindicator 1840 is placed so that when the bat 1810 is placed in thefixture 1800, the dial indicator 1840 contacts the bat 1810 near theload arm 1830. Positioned at or near the free end of the load arm 1830is a load cell 1850. The load cell 1850 produces a specified load on thefree end of the load arm 1840. The distance between the pivot point atthe center of the pivot pin 1832 and the point on the load arm 1830where the load cell 1850 acts is designated as dimension “A”. Thedistance between the pivot point at the center of the pivot pin 1832 andthe point where the load arm 1830 contacts the bat 1810 is designated asdimension “B”. The distance between the end of the base 1820 nearest theupright 1822 and the datum 1824 is designated as dimension “C”. Ofcourse, different embodiments of the fixture 1800 have differentdimensions (A, B, C). In the one embodiment shown in FIG. 18, thedimensions are as follows:

[0068] A=17{fraction (9/16)} inches

[0069] B=2¾ inches

[0070] C=4 inches

[0071] In operation, a procedure is set up to test the bat 1810 forflexibility. The procedure includes placing the bat in the fixture 1800.The bat 1810 is placed on the base 1820 and in contact with datum 1824.Next, the load cell 1850 applies 10 pounds of force at load end or freeend of the load arm 1830. The dial indicator 1840 and the load cell 1850are each zeroed. Next, the load cell 1850 applies 60 pounds of force atload end or free end of the load arm 1830. The dial indicator 1840 isthen read to determine the amount of deflection of the bat at the pointor in the area where the load arm 1830 contacts the bat 1810. Thisprocedure is repeated a number of times around the circumference of thebat 1810. The average value is then used to determine a number toindicate the flexibility of the bat 1810. One example of a calculationof such a number includes dividing the load placed on the arm by theload cell 1850 by the amount of deflection indicated by the dialindicator 1840. In this example, the load of 60 lbs is divided by thedeflection in inches (60 lbs./0.0575″=1043 lbs./in or 1043 Flex) toyield a flex indication number of 1043. It is contemplated that othertesters or fixtures could be used to determine flexibility of the bat1810 under test without departing from the spirit of this invention.

[0072] Of course, the amount flexibility of a bat is linked to batperformance. Performance is also determined by the distance a standardASA softball can be hit as well as the amount of “sting” or vibrationwithin the bat. Using the fixture 1810 described in the example abovebats having a flexibility value in the range of 600 to 1200 have goodperformance characteristics. Bats having a flexibility in the range of1000 to 1200 units also have good performance characteristics.

[0073] Advantageously, the composite material has a lower density thanmetals used to make bats, such as aluminum or titanium. As a result,more material can be used resulting in a more durable bat for a givenweight of bat. The composites also have a higher strength than aluminumand titanium and their alloys. Therefore, a stronger bat can beproduced. In addition, the composite does not dent and therefore moreenergy is transferred to the ball. There is less, if any, energy wastedon denting the bat or the inner sleeve. Therefore, the inventive bathits farther than a wooden or metal bat or bat having metal parts. Theadditional flexibility of the composite material forms a bat with higherperformance which hits better. Furthermore, the inventive bat has adurability advantage since the bat does not dent.

[0074] It is to be understood that the above description is intended tobe illustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reviewing the abovedescription. The scope of the invention should, therefore, be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

What is claimed is:
 1. A bat comprising: a hitting surface; a handleelement attached to the hitting surface; a first sleeve positionedwithin the hitting surface; and a second sleeve positioned within thehitting surface, wherein the hitting surface.
 2. The bat of claim 1wherein the first sleeve and the second sleeve are comprised ofcomposite materials.
 3. The bat of claim 2 wherein the hitting surfacehas a first stiffness and one of the first sleeve and the second sleevepositioned within the hitting surface has a second stiffness differentthan the first stiffness.
 4. The bat of claim 2 wherein the hittingsurface is made from a first set of fibers and a first resin and whereinthe first sleeve and second sleeve are made from a second set of fibersand a second resin, the second set of fibers and the second resin beingdifferent than the first set of fibers and first resin.
 5. The bat ofclaim 4 wherein the second fiber and resin is impregnated in the secondset of fibers.
 6. The bat of claim 4 wherein the second set of fibersand resin is a sheet of material.
 7. The bat of claim 1 wherein thesecond sleeve is formed on the first sleeve.
 8. The bat of claim 1wherein the first sleeve is separated from the first sleeve by a layerof material.
 9. The bat of claim 2 wherein the first sleeve is separatedfrom the second sleeve by a layer of a release material.
 10. A batcomprising: a hitting surface further including; a first wall; a secondwall; and a third wall; and a handle element attached to the hittingsurface.
 11. The bat of claim 10 wherein the hitting surface is in theshape of a barrel.
 12. The bat of claim 10 wherein the first wall ismade of a first material and the second wall is made of a secondmaterial.
 13. The bat of claim 12 wherein the first material is metal.14. The bat of claim 12 wherein the first material is a compositematerial.
 15. The bat of claim 10 wherein the second wall and the thirdwall are made of the same materials.
 16. The bat of claim 10 wherein thesecond wall and the third wall are made of different materials.
 17. Thebat of claim 10 wherein the bat has a flexibility of greater than 600.18. A bat comprising: a hitting surface having a flexibility within therange of 600 to 1300; and a handle attached to the hitting surface. 19.The bat of claim 18 wherein the flexibility is within the range of 800to
 1200. 20. The bat of claim 18 wherein the flexibility is within therange of 950 to
 1150. 21. A method of forming a bat having a handle anda hitting surface, the method comprising: forming a first sleeve;forming a second sleeve; and fitting the first sleeve and the secondsleeve within the hitting surface.
 22. The method of claim 21 whereinthe first sleeve is formed of metal.
 23. The method of claim 21 whereinthe first sleeve and the second sleeve are formed of metal.
 24. Themethod of claim 21 wherein the first sleeve is formed of a compositematerial.
 25. The method of claim 21 wherein the first sleeve and thesecond sleeve are formed of a composite material.
 26. The method ofclaim 21 wherein the step of forming a first sleeve and a forming asecond sleeve further comprises: laying up a first plurality of layersof material; covering the first plurality of layers of material with arelease material; and laying up a second plurality of layers ofmaterial.
 27. The method of claim 26 wherein covering the firstplurality of layers with a release material includes covering the firstplurality of layers with polypropylene.
 28. The method of claim 25wherein forming a first sleeve includes wrapping a plurality of layersabout a mandrel and wherein, forming a second sleeve includes wrapping aplurality of layers about a mandrel.
 29. The method of claim 21 furthercomprising: loading a portion of the bat; and measuring the amount ofdeflection.
 30. The method of claim 29 wherein loading a portion of thebat includes placing a force on the hitting surface of the bat.
 31. Themethod of claim 29 wherein loading a portion of the bat includes placinga force on the surface of the bat having a first sleeve and a secondsleeve.
 32. The method of claim 29 wherein loading a portion of the batincludes placing a force on a plurality of areas associated with thehitting surface of the bat.
 33. The method of claim 32 wherein measuringthe amount of deflection includes measuring the deflection at theplurality of areas associated with the hitting surface of the bat. 34.The method of claim 32 wherein measuring the amount of deflectionincludes measuring the deflection at the plurality of areas associatedwith the hitting surface of the bat, the method further comprisingaveraging the amount of deflection for each of the measured areas. 35.The method of claim 34 wherein loading the hitting surface at theplurality of areas includes placing substantially the same load on eachof the plurality of areas of the hitting surface.
 36. The method ofclaim 32 further comprising dividing the load placed on the bat by themeasured deflection to yield a number representing flexibility of thebat.
 37. The method of claim 32 further comprising: dividing the loadplaced on the bat by the measured deflection to yield a numberrepresenting flexibility of the bat; determining a number representingflexibility at a plurality of points on the bat; and averaging thedetermined flexibility numbers.
 38. The method of claim 37 wherein theflexibility numbers are determined for a hitting surface of the bat. 39.The method of claim 37 wherein the load placed on the bat issubstantially equal at the various portions of the bat.
 40. A method offorming a bat having a handle and a hitting surface, the methodcomprising: forming a hitting surface; and forming a plurality ofsleeves adjacent the hitting surface.